Semiconductor constructions; and methods of forming semiconductor constructions

ABSTRACT

The invention includes a semiconductor construction comprising a semiconductor substrate, and a first layer comprising silicon and nitrogen over the substrate. A second layer comprising at least 50 weight % carbon is over and physically against the first layer, and a third layer consisting essentially of a photoresist system is over and physically against the second layer. The invention also includes methodology for forming the semiconductor construction.

TECHNICAL FIELD

[0001] The invention pertains to semiconductor constructions and methodsof forming semiconductor constructions. In particular aspects, theinvention pertains to semiconductor constructions in which an organicmaterial is provided between photoresist and a layer comprising siliconand nitrogen, and to methods of forming such constructions.

BACKGROUND OF THE INVENTION

[0002] Photolithography is a commonly-used method for patterningfeatures during semiconductor processing. A photosensitive material(photoresist) is formed over a mass which is ultimately to be patterned,and the photoresist is subsequently subjected to radiation. Theradiation is provided in a pattern so that some portions of thephotoresist are impacted by the radiation while other portions of thephotoresist are not impacted by the radiation. The photoresist is thensubjected to developing conditions which selectively remove either theimpacted or non-impacted portions. If the photoresist is a positivephotoresist, the impacted portions are selectively removed; and if thephotoresist is a negative photoresist, the non-impacted portions areselectively removed.

[0003] The photoresist remaining after the development defines apatterned mask. The pattern of the mask can subsequently be transferredto the underlying mass utilizing appropriate etching conditions to formpatterned features within the mass.

[0004] A difficulty which can be encountered during photolithographicprocessing is that the radiation utilized to pattern the photoresist(typically light) can be reflected from the underlying mass to causevarious constructive and destructive interference patterns to occur inthe light as it passes through the photoresist. This can adverselyaffect a pattern ultimately developed in the photoresist.

[0005] The problem is typically addressed by providing an antireflectivecoating immediately beneath the photoresist. Various antireflectivecoatings have been developed, with a deposited antireflective coating(DARC) being exemplary. Deposited antireflective coatings will typicallycomprise silicon and nitrogen, and can, for instance, consist of, orconsist essentially of, silicon, nitrogen and optionally, hydrogen.DARC's can alternatively comprise silicon, oxygen, and in some cases,hydrogen, and can be referred to as silicon oxynitride materials.

[0006] DARC materials can be particularly useful as antireflectivecoatings during photolithographic processing of metals, and/orinsulative materials (with an exemplary insulative material beingborophosphosilicate glass).

[0007] An exemplary photolithographic fabrication process utilizing aDARC material is described with reference to FIGS. 1 and 2. Referringinitially to FIG. 1, a fragment of a semiconductor construction 10 isillustrated at a preliminary processing stage. Construction 10 comprisesa substrate 12. Substrate 12 can include, for example, a semiconductivematerial (such as, for example, monocrystalline silicon). To aid ininterpretation of the claims that follow, the terms “semiconductivesubstrate” and “semiconductor substrate” are defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

[0008] A mass 14 is supported by substrate 12. Mass 14 can comprise aninsulative material (such as, for example, borophosphosilicate glass)and/or various metals and/or metal compounds. Mass 14 is shown as asingle uniform layer, but it is to be understood that mass 14 cancomprise stacks of various materials.

[0009] An antireflective coating layer 16 is shown formed over mass 14.Layer 16 will preferably comprise a DARC, such as, for example, siliconoxynitride.

[0010] A photoresist 18 is shown formed over and physically againstantireflective coating 16.

[0011] Radiation 20 is shown impacting various regions of photoresist18. Radiation 20 will typically comprise light, and can, for example,predominately comprise light having a wavelength which is in the regionof from about 150 nanometers to about 250 nanometers. Regions ofphotoresist 18 impacted by radiation 20 are illustrated generally withthe label 22, and regions of the photoresist 18 which are not impactedby radiation 20 are illustrated generally with the label 24.

[0012] Photoresist 18 can comprise a chemically amplified photoresist.In such application, radiation 20 will create a photogenerated catalyst(typically a strong acid) within regions 22 of the photoresist. Thephotoresist is then subjected to a post-exposure bake wherein thephotogenerated catalyst causes further reactions to alter solubility ofexposed regions 22 (and in some applications regions proximate exposedregions 22) relative to regions 24 in a developer solution. An advantageof utilizing chemically amplified photoresists is that such can increasethe sensitivity of photoresist to radiation by enabling a singleincident photon to be responsible for many chemical events.

[0013] Photoresist 18 can be referred to as a photoresist system toindicate that the photoresist can comprise various components ultimatelyaffected by exposure of a portion of photoresist 18 to light. Forinstance, if material 18 comprises a chemically amplified photoresistsystem, it will typically comprise a photoactive species whichultimately forms a photocatalyst (typically an acid) upon exposure tolight having a suitable wavelength. The photoactive species theninteracts with other materials present in the photoresist system toalter chemical properties of the system. The material 18 can be referredto as consisting essentially of a photoresist system to indicate thatthe material 18 consists essentially of components which are patternedduring a photolithographic process to form a mask. Photoresist system 18can, in particular applications, comprise a multilayer resist.

[0014]FIG. 2 illustrates construction 10 after a suitable post-exposurebake, and subsequent exposure to a developing solution. Photoresist 18is illustrated as being a positive photoresist, and accordingly impactedregions 22 (FIG. 1) are selectively removed relative to non-impactedregions 24.

[0015] A problem with utilization of DARC is that such can scavengephotogenerated catalysts (such as acid) during the post-exposure bake ofphotoresist 18, and can accordingly interfere with the patterning of thephotoresist. For instance, the patterned photoresist of FIG. 2 is shownto comprise blocks 30 and 32 and such blocks are wider proximateantireflective coating 16 than at upper surfaces of the blocks. Thewidened regions at the blocks can be referred to as foot portions 34.Such foot portions are undesired.

[0016] It would be desirable to develop photolithographic processingmethods which alleviate or prevent formation of foot portions 34.

SUMMARY OF THE INVENTION

[0017] In one aspect, the invention includes a semiconductorconstruction comprising a semiconductor substrate, and a first layercomprising silicon and nitrogen over the substrate. A second layercomprising at least 50 weight % carbon is over and physically againstthe first layer, and a third layer consisting essentially of aphotoresist system is over and physically against the second layer.

[0018] In another aspect, the invention encompasses a method of forminga semiconductor construction. A semiconductor substrate is provided, anda first layer comprising silicon and nitrogen is formed over thesubstrate. A second layer comprising at least 50 weight % carbon isformed over the first layer, and a third layer consisting essentially ofa photoresist system is formed over and physically against the secondlayer. A first portion of the third layer is exposed to radiation whilea second portion of the third layer is not exposed to the radiation. Thethird layer is subjected to conditions which cause either the exposedfirst portion or unexposed second portion of the photoresist system torelease acid. The second layer also releases acid as the third layer isexposed to the conditions. After the third layer is subjected to theconditions, either the first or second portion is selectively removedrelative to the other of the first and second portion of the photoresistsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0020]FIG. 1 is a diagrammatic, cross-sectional view of a fragment of asemiconductor construction shown at a preliminary stage of a prior artprocessing method.

[0021]FIG. 2 is a view of the FIG. 1 fragment shown at a prior artprocessing stage subsequent to that of FIG. 1.

[0022]FIG. 3 is a diagrammatic, cross-sectional view of a fragment of asemiconductor construction shown at a preliminary stage of an exemplarymethod which can be encompassed by the present invention.

[0023]FIG. 4 is a view of the FIG. 3 fragment shown at a processingstage subsequent to that of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In particular aspects, the invention encompasses provision of anorganic material (for example, a material comprising at least 50 weight% carbon and/or a material comprising carbon-hydrogen bonds) between adeposited antireflective coating layer (or any layer comprising siliconand nitrogen) and photoresist. An exemplary method illustrating aspectsof the invention is described with reference to FIGS. 3 and 4.

[0025] Referring initially to FIG. 3, a wafer construction 50 comprisesa substrate 12 having a mass 14 thereover. Substrate 12 and mass 14 cancomprise identical constructions to those described above with referenceto the prior art of FIGS. 1 and 2.

[0026] An antireflective coating layer 16 is formed over mass 14. Inparticular aspects, mass 14 can comprise an insulative material, suchas, for example, borophosphosilicate glass, and antireflective coatinglayer 16 can be physically against such insulative material. In otheraspects, mass 14 can comprise a metal, such as, for example, titanium,tantalum, tungsten etc., and antireflective coating 16 can be physicallyagainst such metal. In yet further aspects, mass 14 can comprise a metalcompound, such as, for example, tungsten nitride, titanium nitride,tantalum nitride, titanium silicide, etc., and antireflective coatinglayer 16 can be physically against such metal compound. Further,although mass 14 is shown as comprising a single uniform composition, itshould be understood that mass 14 can comprise various substructurestherein, with exemplary substructures being stacks of various materials.

[0027] Antireflective coating layer 16 can comprise, consist essentiallyof, or consist of silicon, nitrogen and optionally, hydrogen.Alternatively, antireflective coating 16 can comprise, consistessentially of, or consist of silicon, nitrogen, oxygen and optionally,hydrogen. Antireflective coating layer 16 can be referred to as a firstlayer provided over a semiconductor substrate comprising the illustratedcomponents 12 and 14.

[0028] A layer 52 is formed over first layer 16. Layer 52 can bereferred to as a second layer formed over the semiconductor substratecomprising components 12 and 14, and in the shown embodiment is formedphysically against an upper surface of first layer 16. Second layer 52is preferably an organic material, and typically comprises at least 50weight % carbon. Layer 52 can comprise a polymer, such as, for example,an acrylic polymer, and further can comprise chemical cross-linksthroughout the polymer. Exemplary polymers include homopolymers andcopolymers comprising polyhydroxyethylmethacrylate,polymethylmethacrylate, substituted polymethylmethacrylate, andpolystyrene.

[0029] Layer 52 can be transparent to radiation which is ultimatelyutilized to pattern a photoresist formed over layer 52, or can comprisecomponents which absorb at least some of the radiation passing throughan overlying photoresist and to layer 52. Typically, the radiationutilized for patterning a photoresist will have a wavelength within aregion of from about 150 nanometers to 250 nanometers, and accordinglylayer 52 can comprise materials which absorb light wavelengths within aregion of from 150 nanometers to 250 nanometers. Suitable materialswhich can be included in layer 52 for absorbing such light are variousdyes and chromophores (which can include chromophores incorporated intoa suitable polymer). Exemplary chromophores can include, for example,benzene rings, anthracene, naphthalene, and coumarine.

[0030] Layer 52 can also comprise one or more materials which generateacid during a bake of photoresist overlying material 52. Suitableacid-generating components are, for example, diazomethane, fluoroalkylsulfonate, alkyl sulfonate, and onium salts.

[0031] Layer 52 can, in particular applications, be spin-coated overlayer 16. In such applications, a surfactant can be provided withinmaterial 52 to improve a uniformity with which material 52 flows acrosslayer 16. Particularly, the surfactant can improve a uniformity withwhich material 52 flows into openings (not shown) penetrating into orthrough layer 16, and can further improve a uniformity with whichmaterial 52 flows over projecting features (not shown) extending from anupper surface that material 52 is spin-coated over. Suitable surfactantscan include, for example, alkyl sulfonium salts, and perfluoroalkylsulfonium.

[0032] Material 52 can further comprise various solvents. For instance,material 52 can be formed by having various polymeric precursors (whichcan include crosslinking materials) suspended or dissolved in a suitablesolvent, and spin-coated over an upper surface of layer 16. Thepolymeric precursors can then be subjected to suitable conditions toform either form a polymeric material from the precursors, or to hardenthe precursors. The solvents can be removed before, during, and/or afterpolymerization of the precursors. It can be desired to remove all of thesolvents, or, it can be acceptable to leave some of the solventsremaining within layer 52 after polymerization. Suitable solvents caninclude, for example, ethyl lactate, methylamylketone,polypropyleneglycol monomethyletheracetate (PGMEA), and propyleneglycolmonomethylether (PGME), in applications in which the polymericprecursors comprise benzoyl peroxide, benzil and/or benzil derivatives,together with cross-linking materials selected from the group consistingof hexamethoxymethirol melamine and tetramethoxyglycouril. Of course,some precursors may exist in a liquid or other form which can beutilized without solvent, and in such applications the polymericprecursors can be provided neat over a surface of layer 16, andsubsequently polymerized.

[0033] A layer 18 comprising, consisting of, or consisting essentiallyof photoresist or a photoresist system is formed over second layer 52.Layer 18 can comprise either positive or negative photoresist, and canbe identical to the layer 18 described above with reference to the priorart illustrated in FIGS. 1 and 2. In particular applications, layer 18comprises a chemically amplified photoresist system.

[0034] In the shown embodiment, layer 18 is formed physically against anupper surface of layer 52. Layer 18 can be referred to as a third layerformed over a semiconductor substrate comprising components 12 and 14.

[0035] Radiation 20 is shown passing into photoresist 18. Radiation 20can comprise the radiation discussed above with reference to prior artFIG. 1, and accordingly can comprise light having a wavelength within arange of from about 150 nanometers to about 250 nanometers. Theradiation impacts regions 22 of resist 18, while other regions 24 ofresist 18 are not exposed to the radiation. Radiation 20 can be referredto as patterned light utilized for photolithography.

[0036] In applications in which photoresist 18 comprises a chemicallyamplified resist, the construction 50 can be subjected to appropriateheating to accomplish a post-exposure bake of construction 50. Asuitable temperature of the post-exposure bake is, for example, 90° C.to 150° C., in applications in which photoresist 18 comprises, forexample, Sumitomo Chemical Co, Ltd, PAR718™, or JSR MicroelectronicsAR360™.

[0037] During the post-exposure bake, a photogenerated catalyst withinregions 22 (typically a strong acid) catalyzes reactions withinphotoresist 18 to change chemical properties within regions 22 relativeto the properties within regions 24. Layer 52 is a barrier betweenphotoresist 18 and antireflective coating 16, and can alleviate orprevent layer 16 from scavenging acid during the post-exposure bake.Further, layer 52 can comprise a suitable component which releases acid,and accordingly enhances acid-catalyzed reactions occurring withinphotoresist 18 during the post-exposure bake. It is noted that layer 52can alternatively, or additionally, be configured to release othercatalysts besides acid which interact with various components ofphotoresist 18.

[0038] After the post-exposure bake, photoresist 18 is exposed to asuitable developing solvent which selectively removes either theportions exposed to radiation 20 (and/or portions exposed to catalystsgenerated by the radiation); or the portions of resist 18 which have notbeen exposed to either radiation or catalysts generated by theradiation. In applications in which resist 18 comprises PAR718™ fromSumitomo Chemical Co, Ltd, of Osaka, Japan, a suitable developingsolvent is OPD 4262™ from Arch Chemicals, Inc., of Norwalk Conn., USA.

[0039]FIG. 4 illustrates construction 50 after exposure to a developingsolvent in applications in which resist 18 comprises a positivephotoresist. The developing solvent has thus removed portions 22 (FIG.3) exposed to radiation. In applications in which resist 18 comprises achemically amplified positive resist system, the solvent can also removeregions of layer 18 proximate to the regions 22 exposed to radiation ifsuch proximate regions are ultimately exposed to catalyst generated fromthe exposed regions 22.

[0040] Resist 18 is shown patterned into blocks 60 and 62, and unlikethe prior art construction 10 of FIG. 2, the blocks do not have footerregions (the regions 34 of FIG. 2). Such footer regions are eitherreduced in size, or, in the shown preferred aspect of the invention,entirely eliminated through utilization of barrier material 52 betweenantireflective coating 16 and photoresist 18.

[0041] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A semiconductor construction, comprising: a semiconductor substrate;a first layer comprising silicon and nitrogen over the substrate; asecond layer comprising at least 50 weight % carbon over and physicallyagainst the first layer; and a third layer consisting essentially of aphotoresist system over and physically against the second layer.
 2. Theconstruction of claim 1 wherein the first layer comprises silicon,oxygen and nitrogen.
 3. The construction of claim 1 wherein the firstlayer consists essentially of silicon oxynitride.
 4. The construction ofclaim 1 wherein the second layer comprises carbon-hydrogen bonds.
 5. Theconstruction of claim 1 wherein the second layer comprises a surfactant.6. The construction of claim 1 wherein the second layer comprises apolymer.
 7. The construction of claim 1 wherein the second layercomprises a cross-linked polymer.
 8. The construction of claim 1 whereinthe second layer comprises an acrylic polymer.
 9. The construction ofclaim 1 wherein the second layer comprises a component that absorbslight having a wavelength within a region from 150 nanometers to 250nanometers.
 10. The construction of claim 1 wherein the photoresistsystem comprises a chemically-amplified photoresist.
 11. A semiconductorconstruction, comprising: a semiconductor substrate; a first layercomprising silicon and nitrogen over the substrate; a second layer overand physically against the first layer, the second layer being anorganic material comprising carbon-hydrogen bonds; and a third layerconsisting essentially of a photoresist system over and physicallyagainst the second layer.
 12. The construction of claim 11 wherein thefirst layer comprises silicon, oxygen and nitrogen.
 13. The constructionof claim 11 wherein the first layer consists essentially of siliconoxynitride.
 14. The construction of claim 11 wherein the second layercomprises a polymer.
 15. The construction of claim 11 wherein the secondlayer comprises a cross-linked polymer.
 16. The construction of claim 11wherein the second layer comprises an acrylic polymer.
 17. Theconstruction of claim 11 wherein the second layer comprises a componentthat absorbs light having a wavelength within a region from 150nanometers to 250 nanometers.
 18. The construction of claim 11 whereinthe photoresist system comprises a chemically-amplified photoresist. 19.A method of forming a semiconductor construction, comprising: providinga semiconductor substrate; forming a first layer comprising silicon andnitrogen over the substrate; forming a second layer comprising at least50 weight % carbon over and physically against the first layer; andforming a third layer consisting essentially of a photoresist systemover and physically against the second layer.
 20. The method of claim 19further comprising exposing the photoresist system to patterned lightand subsequently heating the photoresist system; the second layerreleasing acid into the photoresist system during the heating; after theheating, exposing the photoresist system to a developing solvent. 21.The method of claim 19 wherein the first layer comprises silicon, oxygenand nitrogen.
 22. The method of claim 19 wherein the first layerconsists essentially of silicon oxynitride.
 23. The method of claim 19wherein the forming the second layer comprises spin-coating the secondlayer across the first layer.
 24. The method of claim 19 wherein thesecond layer comprises a surfactant.
 25. The method of claim 19 whereinthe second layer comprises a polymer.
 26. The method of claim 19 whereinthe second layer comprises a cross-linked polymer.
 27. The method ofclaim 19 wherein the second layer comprises an acrylic polymer.
 28. Themethod of claim 19 wherein the second layer comprises a component thatabsorbs light having a wavelength within a region from 150 nanometers to250 nanometers.
 29. A method of forming a semiconductor construction,comprising: providing a semiconductor substrate; forming a first layercomprising silicon and nitrogen over the substrate; forming a secondlayer comprising at least 50 weight % carbon over the first layer;forming a third layer consisting essentially of a photoresist systemover and physically against the second layer; exposing a first portionof the third layer radiation while not exposing a second portion to theradiation; subjecting the third layer to conditions which cause eitherthe exposed first portion or unexposed second portion of the photoresistsystem to release acid; the second layer also releasing acid as thethird layer is exposed to the conditions; and after subjecting the thirdlayer to the conditions, removing either the first or second portionselectively relative to the other of the first and second portion. 30.The method of claim 29 wherein the conditions which cause either theexposed first portion or unexposed second portion of the photoresistsystem to release acid comprise heating of the third layer to atemperature of at least about 90° C.
 31. The method of claim 29 whereinthe first layer comprises silicon, oxygen and nitrogen.
 32. The methodof claim 29 wherein the first layer consists essentially of siliconoxynitride.
 33. The method of claim 29 wherein the forming the secondlayer comprises spin-coating the second layer across the first layer.34. The method of claim 29 wherein the second layer comprises asurfactant.
 35. The method of claim 29 wherein the second layercomprises a polymer.
 36. The method of claim 29 wherein the second layercomprises a cross-linked polymer.
 37. The method of claim 29 wherein thesecond layer comprises an acrylic polymer.
 38. The method of claim 29wherein the second layer comprises a component that absorbs light havinga wavelength within a region from 150 nanometers to 250 nanometers.